The standard of care in caregiver environments includes patient monitoring through spectroscopic analysis using, for example, a pulse oximeter. Devices capable of spectroscopic analysis generally include a light source(s) transmitting optical radiation into or reflecting off a measurement site, such as, body tissue carrying pulsing blood. After attenuation by tissue and fluids of the measurement site, a photodetection device(s) detects the attenuated light and outputs a detector signal(s) responsive to the detected attenuated light. A signal processing device(s) process the detector(s) signal(s) and outputs a measurement indicative of a blood constituent of interest, such as glucose, oxygen, methemoglobin, total hemoglobin, other physiological parameters, or other data or combinations of data useful in determining a state or trend of wellness of a patient.
In noninvasive devices and methods, a sensor is often adapted to position a finger proximate the light source and light detector. For example, noninvasive finger clip sensors often include a clothespin-shaped housing that includes a contoured bed conforming generally to the shape of a finger.
Accurate determination of physiological measurements is often dependent upon proper application of the optical sensor to the measurement site. Clip-type pulse oximeter sensors typically include a physical stop near the hinge of the housing to indicate desired placement of a user's finger or other measurement site within the sensor. However, the physical stop does not ensure that the patient's finger is positioned far enough into the sensor. In addition, even if a sensor is initially placed correctly, movement, either of the patient or of the sensor during artificial pulsing, can longitudinally displace the patient's finger within the sensor. This can result in the light source and detector of the oximeter being positioned around a portion of the finger that provides inaccurate physiological measurements.